AM methods are known to be used to fabricate models of three-dimensional objects, including biological organs. AM or Solid Freeform Fabrication (SFF) is a technology enabling fabrication of arbitrarily shaped structures directly from computer data via additive formation steps. The basic operation of any SFF system consists of slicing a three-dimensional computer model into thin cross sections, translating the result into two-dimensional position data and feeding the data to control equipment which fabricates a three-dimensional structure in a layerwise manner.
Methods for using tomography data, e.g. data provided by a Computer Tomography (CT) scanner or Magnetic Resonance Image (MRI) machine to physically reconstruct a biological organ by AM are also known. The tomography data typically includes grayscale image data of cross sections of the scanned biological organ. Typically, the tomography data is provided in a Digital Imaging and Communications in Medicine (DICOM) file format.
In known physical reconstructing methods, a Computer Aided Design (CAD) system is used to convert and/or translate the DICOM file to a three-dimensional computer model in the form of a StereoLithography (STL) file that can be read by AM devices. STL files only describe surface geometry of a three dimensional object without any representation of possible variations in color, texture and/or mechanical properties within the volume of the three dimensional object. Since variations within the volume cannot be represented with an STL file, much of the information included in the DICOM file is lost during the translation.
U.S. Pat. No. 5,768,134 entitled “Method for making a perfected medical model on the basis of digital image information of a part of the body” incorporated herein by reference in its entirety, describes a method for adding an artificial function element to a model of a body part based on digital image information, e.g. in a CT image prior to segmentation. As described therein, the artificial function element that is added is a function of the digital image information in the form in which all medical data are visible, before segmenting image data pertaining to the body part from the rest of the image. It is described by way of example that a function element, such as an opening indicating the place and direction for boring, can be added as a function of the image information showing additional elements surrounding the body part. It is also described that external information coming from the medical user may be added to the image information and the artificial functional element may also be a function of this additional external information.
US Patent Publication No. 20100191360 entitled “Solid freeform fabrication using a plurality of modeling materials,” assigned to the common assignee and incorporated herein by reference in its entirety, describes inter alia a system and method for fabricating objects using two or more modeling materials in different predetermined combinations, wherein the combinations are produced by dispensing different modeling materials from different dispensing heads. The different modeling materials may be dispensed in different locations within a layer or may be dispensed in same location or adjacent locations so as to allow formation of a composite material.
There is also described a method for defining composite material structures without the need for standard CAD software in order to design the full three-dimensional structure. The method described includes performing a Boolean comparison between bitmaps representing the desired composite material structure and bitmaps produced by STL files representing the three-dimensional object. It is stated that by eliminating the need for standard CAD software for creating a bitmap representation of the desired composite material structure, the time that would be required for the design process is saved as well as computer memory resources which would usually be required in order to design three-dimensional structures and for the analysis of such three-dimensional structure during the building process.
It is further described that the two or more building and/or modeling materials can include a non-solidifiable material that remains in liquid, gel, paste or other non-solid or semi-solid form. Optionally, a second solidifiable material can fully surround or contain the non-solidifiable material during fabrication so that the non-solidifiable material can remain within the object, or alternatively be drained, burnt-out or otherwise removed once the process is complete. In this way it is described that a hollow or porous model can be provided.